Wall Street got its hopes up on Mar. 11. Elated by a Federal Reserve move to stop the credit crunch, the U.S. stock market posted its biggest one-day gain in five years, with the Dow Jones industrial average rising more than 400 points. Look out, though. Fed officials are the first to acknowledge that their initiative attacks only one problem, the liquidity squeeze at big banks. It does nothing about the central risk to the U.S. economy: an unprecedented crash in home values.

　　How bad will this downturn get No one can know because we've never experienced such a headlong slide in the housing market—and this comes at a time when its current value of $20 trillion accounts for the vast majority of most families' wealth. Right now most economists expect the U.S. to experience a mild, short recession in 2008. But there is at least a possibility of a steeper decline that the traditional recession remedies—interest-rate cuts here, deficit spending there—won't be able to handle.